2-Azaanthraquinones have been rarely found in nature and so far, only a few naturally occurring 2-azaanthraquinones have been reported. Nevertheless, also these compounds have been found to possess interesting physiological activities. Therefore, the search for new effective methods for their synthesis has elicited considerable interest. Since the Pictet-Spengler is a powerful methodology for the construction of the tetrahydroisoquinoline skeleton we decided to apply this reaction as the key step for the preparation of 2-azaanthraquinones.
The first strategy consists of the synthesis of substituted 1,4-dimethoxynapht-2-ylethylamine, followed by Pictet-Spengler condensation with formaldehyde under hydrochloric acid catalysis and a subsequent oxidation - aromatization using silver (II) oxide in the presence of nitric acid. The demethylated compound was only stable under its salt form, since the free amine underwent unselective oxidation in the air over one hour at room temperature.
In a second approach, N-acyl derivatives of tetrahydrobenz[g]isoquinolines were prepared starting from amine (R = H) via condensation of with an aldehyde RCHO to give imines, which were converted in situ to the corresponding N-acyliminium ions, and finally cyclized under Lewis acid catalysis. After screening of a wide variety of Lewis acids the best conversions were observed with AlCl3. The oxidative demethylation of compounds is under investigation. The reaction of i-Pr-substituted imine with acetyl chloride in the absence of a Lewis acid resulted in the formation of compound.
Original languageEnglish
Title of host publication23rd European Colloquium on heterocyclic chemistry, September 9-13 2008 (Antwerp, Belgium)
Pages158
Number of pages1
Publication statusPublished - 9 Sep 2008
EventFinds and Results from the Swedish Cyprus Expedition: A Gender Perspective at the Medelhavsmuseet - Stockholm, Sweden
Duration: 21 Sep 200925 Sep 2009

Conference

ConferenceFinds and Results from the Swedish Cyprus Expedition: A Gender Perspective at the Medelhavsmuseet
CountrySweden
CityStockholm
Period21/09/0925/09/09

    Research areas

  • Pictet-Spengler, 2-azaanthraquinones, napthalenes, napthoquinones

ID: 1715747